Gatlin won the 100m title at the Athens Olympics in 2004

Gatlin wants to compete in June's US trials ahead of this summer's Games.

The 25-year-old was suspended for four years in January after a positive test for testosterone in 2006 was deemed a second offence.

He claims a 2001 positive for drugs taken for attention deficit disorder should not have counted against him.

Gatlin was initially banned for eight years by the United States Anti-Doping Agency (Usada) but it was reduced to four years after an appeal in January.

Punishing Justin for taking medicine that was prescribed by a doctor and does not enhance performance in any way is unfair Gatlin's attorney Maurice Suh

His appeal to the Court of Arbitration for Sport (Cas) claims that any enhancement of the 2006 case caused by the first positive test constitute a violation of the Americans with Disabilities Act.

"Justin should be allowed to compete in the June's US trials for the Beijing Olympics because the anti-doping authorities violated the Americans with Disabilities Act when it sanctioned Justin in 2001 for taking attention-deficit disorder medication and later used that sanction to bar him from participating in the Olympics," said Gatlin's attorney Maurice Suh.

"Punishing Justin for taking medicine that was prescribed by a doctor and does not enhance performance in any way is unfair and constitutes discrimination against a person with a diagnosed disability," added Suh.

Had the US panel, in a split decision, not considered the 2001 test in its verdict, Gatlin may have received a two-year suspension as a first-time offender.

That would have made him eligible to return to competition in May, a month before the US Olympic trials.